Merge: tracing: Add division and multiplication support for hist triggers [rhel-9]

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6586

# Merge Request Required Information

JIRA: https://issues.redhat.com/browse/RHEL-67679

## Summary of Changes

Backport support for division and multiplication in histogram triggers as well as fixes and optimizations for it. Support for creating hist trigger variables from literal is added, too, as it is a dependency of one of the fixes and is documented together with the former.

## Approved Development Ticket(s)
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Signed-off-by: Tomas Glozar <[email protected]>

Approved-by: Joe Lawrence <[email protected]>
Approved-by: Waiman Long <[email protected]>
Approved-by: CKI KWF Bot <[email protected]>

Merged-by: Augusto Caringi <[email protected]>

Author: caringi

Documentation/trace/histogram.rst

@@ -1762,6 +1762,20 @@ using the same key and variable from yet another event::
 
   # echo 'hist:key=pid:wakeupswitch_lat=$wakeup_lat+$switchtime_lat ...' >> event3/trigger
 
+Expressions support the use of addition, subtraction, multiplication and
+division operators (+-\*/).
+
+Note that division by zero always returns -1.
+
+Numeric constants can also be used directly in an expression::
+
+  # echo 'hist:keys=next_pid:timestamp_secs=common_timestamp/1000000 ...' >> event/trigger
+
+or assigned to a variable and referenced in a subsequent expression::
+
+  # echo 'hist:keys=next_pid:us_per_sec=1000000 ...' >> event/trigger
+  # echo 'hist:keys=next_pid:timestamp_secs=common_timestamp/$us_per_sec ...' >> event/trigger
+
 2.2.2 Synthetic Events
 ----------------------